Color filter on array substrate having a photoresist plug contacting a liquid crystal layer

ABSTRACT

A COA substrate manufacturing method including: forming a TFT on a base substrate; forming a second insulation layer on the TFT; forming a color resist layer on the second insulation layer; forming a third insulation layer on the color resist layer; forming a through hole which exposes the drain electrode of the TFT; forming an ITO film layer on the third insulation layer; forming a photoresist layer on the ITO film layer; performing a light-shielding process to the photoresist layer on the vias-region ITO film layer and an exposure process to the photoresist layer on the non vias-region ITO film layer; developing the photoresist layer on the vias-region ITO and the non vias-region ITO film layers to obtain a photoresist layer plug covered on the vias-region ITO film layer. The photoresist is provided to fill the through hole so as to improve the quality of a display device.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of co-pending patent application Ser.No. 14/908,808, filed on Jan. 27, 2016, which is a national stage of PCTApplication Number PCT/CN2015/099148, filed on Dec. 28, 2015, claimingforeign priority of Chinese Patent Application Number 201510697888.3,filed on Oct. 23, 2015.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a liquid crystal display field, andmore particularly to a display device, a COA substrate and amanufacturing method for the same.

2. Description of Related Art

The technology adopted by a COA (Color Filter on Array) substrate is tointegrate a color filter into an array substrate. Comparing withconventional alignment technology of a CF (color filter) substrate and aTFT (thin-film transistor), the COA technology provides a designstrategy for decreasing a difficulty of alignment process of amanufacturing process for a display panel. Specifically, in theconventional technology, in order to eliminate an alignment error asmuch as possible, a wider black matrix (BM) is adopted to shield alight. However, in a COA substrate, the black matrix can be designed asa narrow trace width so that aperture ratio is increased. In addition,the COA substrate increases a distance between a pixel electrode and ametal trace through a photoresist layer so as to reduce a capacitivecoupling effect of the pixel electrode and the metal trace so that asignal delay effect on the metal line can be improved to improve thepanel quality.

However, when the COA substrate increases the distance between the metaltrace and the pixel electrode, a connection difficulty between the pixelelectrode and the metal trace is also increase. Specifically, betweenthe pixel electrode and the metal trace, two insulation layers and acolor filter exist, a very deep through hole is required. In orderprevent breaking of the trace of the pixel electrode or a poor contactamong metal trace, an opening area of the through hole is larger. In asubsequent process, when liquid crystals drop, the liquid crystals areeasily to gather at the location of the trough hole so that thedeflection of the liquid crystals near the through hole is notcontrolled by a voltage, which causes an abnormal display and affectsthe quality of the panel of the display device.

In summary, it is necessary to provide a display device, a COA substrateand a manufacturing method for the same to solve the above problems.

SUMMARY OF THE INVENTION

The main technology problems are solved by the present invention thatprovides a display device, a COA substrate and a manufacturing methodfor the same in order to improve the quality of the panel of the displaydevice.

In order to solve above technology problem, a technology solutionadopted by the present invention is: a Color Filter on Array (COA)substrate manufacturing method comprising: forming a thin-filmtransistor on a base substrate, wherein the thin-film transistorincludes a first metal layer on the base substrate, a first insulationlayer disposed on the first metal layer, a semiconductor active layerdisposed on the first insulation layer, and a second metal layerdisposed on the semiconductor active layer, the second metal layer formsa drain electrode of the thin-film transistor; forming a secondinsulation layer on the thin-film transistor; forming a color resistlayer on the second insulation layer; forming a third insulation layeron the color resist layer; forming at least one through hole whichreveals the drain electrode of the thin-film transistor; wherein themethod further comprises: forming an ITO film layer on the thirdinsulation layer, wherein the ITO film layer includes a vias-region ITOfilm layer located on the through hole and a non vias-region ITO filmlayer located outside the through hole; forming a photoresist layer onthe ITO film layer; performing a light-shielding process to thephotoresist layer on the vias-region ITO film layer, and performing anexposure process to the photoresist layer on the non vias-region ITOfilm layer; developing the photoresist layer on the vias-region ITO filmlayer and the photoresist layer on the non vias-region ITO film layer inorder to obtain a photoresist layer plug covered on the vias-region ITOfilm layer.

In the above solution, the non vias-region ITO film layer includes atrace-region ITO film layer and a non trace-region ITO film layer; andthe step of performing an exposure process to the photoresist layer onthe non vias-region ITO film layer includes: performing a partialexposure process to the photoresist layer on the trace-region ITO filmlayer in order to partially remove the photoresist layer on thetrace-region ITO film layer, and performing a full exposure process tothe photoresist layer on the non trace-region ITO film layer in order tocompletely remove the photoresist layer non trace-region ITO film layer.

In the above solution, the step of performing a partial exposure processto the photoresist layer on the trace-region ITO film layer includes:using a semi-transparent mask to perform a semi-exposure process to thephotoresist layer on the trace-region ITO film layer.

In the above solution, after the step of developing the photoresistlayer on the vias-region ITO film layer, the method further includes:using an etching process to remove the non trace-region ITO film layer.

In the above solution, after the step of using an etching process toremove the non trace-region ITO film layer, the method further includes:

using a dry etching process to the photoresist layer on the trace-regionITO film layer and the photoresist layer on the vias-region ITO filmlayer in order to completely remove the photoresist layer on thetrace-region ITO film layer, and partially remove the photoresist layeron the vias-region ITO film layer such that the photoresist layer plugis covered on the through hole.

In the above solution, a side plane of the photoresist layer plugexposed outside the through hole is perpendicular to the base substrate.

In the above solution, the first metal layer forms a gate electrode ofthe thin-film transistor, and the second metal layer forms a sourceelectrode of the thin-film transistor.

In order to solve above technology problem, another technology solutionadopted by the present invention is: a Color Filter on Array (COA)substrate comprising: a base substrate; a thin-film transistor disposedon the base substrate, wherein the thin-film transistor includes a firstmetal layer disposed on the base substrate, a first insulation layerdisposed on the first metal layer, a first insulation layer disposed onthe first metal layer, a semiconductor active layer disposed on thefirst insulation layer and a second metal layer disposed on thesemiconductor active layer, and the second metal layer forms a drainelectrode of the thin-film transistor; a second insulation layerdisposed on the thin-film transistor, a color resist layer disposed onthe second insulation layer; a third insulation layer disposed on thecolor resist layer and at least one through hole which reveals the drainelectrode of the thin-film transistor; wherein, the COA substratefurther includes: a ITO film layer disposed on the third insulationlayer, wherein the ITO film layer includes a vias-region ITO film layeron the through hole; and a photoresist layer plug covered on thevias-region ITO film layer.

In the above COA substrate, the photoresist layer plug includes a plugportion and a protrusion portion, the plug portion is filled in thethrough hole, and the protrusion portion is protruded out from thethrough hole.

In the above COA substrate, the protrusion portion includes a horizontalplane in parallel with the base substrate and a side plane perpendicularto the base substrate.

In the above COA substrate, the protrusion portion includes a horizontalplane in parallel with the base substrate and a side plane forming aninclined angle with respect to the base substrate.

In the above COA substrate, the inclined angle formed between the sideplane and the base substrate is less than 30 degrees.

In the above COA substrate, the first metal layer forms a gate electrodeof the thin-film transistor, and the second metal layer forms a sourceelectrode of the thin-film transistor.

In order to solve the above technology problem, another technologysolution adopted by the present invention is: a display device includinga Color Filter on Array (COA) substrate comprising: a base substrate; athin-film transistor disposed on the base substrate, wherein thethin-film transistor includes a first metal layer disposed on the basesubstrate, a first insulation layer disposed on the first metal layer, afirst insulation layer disposed on the first metal layer, asemiconductor active layer disposed on the first insulation layer and asecond metal layer disposed on the semiconductor active layer, and thesecond metal layer forms a drain electrode of the thin-film transistor;a second insulation layer disposed on the thin-film transistor, a colorresist layer disposed on the second insulation layer; a third insulationlayer disposed on the color resist layer and at least one through holewhich reveals the drain electrode of the thin-film transistor; wherein,the COA substrate further includes: a ITO film layer disposed on thethird insulation layer, wherein the ITO film layer includes avias-region ITO film layer on the through hole; and a photoresist layerplug covered on the vias-region ITO film layer.

In the above display device, the photoresist layer plug includes a plugportion and a protrusion portion, the plug portion is filled in thethrough hole, and the protrusion portion is protruded out from thethrough hole.

In the above display device, the protrusion portion includes ahorizontal plane in parallel with the base substrate and a side planeperpendicular to the base substrate.

In the above display device, the protrusion portion includes ahorizontal plane in parallel with the base substrate and a side planeforming an inclined angle with respect to the base substrate.

In the above display device, the inclined angle formed between the sideplane and the base substrate is less than 30 degrees.

In the above display device, the first metal layer forms a gateelectrode of the thin-film transistor, and the second metal layer formsa source electrode of the thin-film transistor.

The beneficial effects of the present invention is: comparing with theprior art, the manufacturing method for the COA substrate of the presentinvention includes: forming a TFT on a base substrate; forming a secondinsulation layer on the TFT; forming a color resist layer on the secondinsulation layer; forming a third insulation layer on the color resistlayer; forming a through hole which reveals the drain electrode of theTFT; forming an ITO film layer on the third insulation layer; forming aphotoresist layer on the ITO film layer; performing a light-shieldingprocess to the photoresist layer on the vias-region ITO film layer andan exposure process to the photoresist layer on the non vias-region ITOfilm layer; developing the photoresist layer on the vias-region ITO andthe non vias-region ITO film layers to obtain a photoresist layer plugcovered on the vias-region ITO film layer. Through above way, withoutadding a mask, only partially modifying the ITO mask, and using asemi-exposure process to manufacture the pixel electrode of the COAsubstrate, and using the photoresist to fill the opening of the throughhole so as to optimize the manufacturing process of the panel andeffectively improve the panel quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a manufacturing method for a COA substrate ofthe present invention;

FIG. 2 is a schematic structure diagram of a COA substrate of thepresent invention;

FIG. 3 is a schematic enlarged structure diagram of a region A in FIG. 2according to a first embodiment; and

FIG. 4 is a schematic enlarged structure diagram of a region A in FIG. 2according to a second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will combine figures and embodiments for describing thepresent invention in detail.

As shown in FIG. 1, FIG. 1 is a flowchart of a manufacturing method fora COA substrate of the present invention. The method includes followingstep:

Step S101: forming a thin-film transistor on a base substrate;

wherein the thin-film transistor (TFT) includes a first metal layer onthe base substrate, a first insulation layer disposed on the first metallayer, a semiconductor active layer disposed on the first insulationlayer, and a second metal layer disposed on the semiconductor activelayer; and the first metal layer forms a gate electrode of the TFT, thesecond metal layer forms a drain electrode and a source electrode of theTFT.

Step S102: forming a second insulation layer on the thin-filmtransistor.

Step S103: forming a color resist layer on the second insulation layer.

Step S104: forming a third insulation layer on the color resist layer.

Step S105: forming at least one through hole which reveals a drainelectrode of the thin-film transistor.

Step S106: forming an ITO film layer on the third insulation layer;

wherein the ITO film layer at the through hole passes through the thirdinsulation layer, the color resist layer and the second insulationlayer, and connects with a signal of the second metal layer; the ITOfilm layer includes a vias-region ITO film layer located on the throughhole and a non vais-region ITO film layer located outside the throughhole. In the present embodiment, a thickness of the ITO film layerattached on the third insulation layer is the same. That is, a thicknessof the vias-region ITO film layer located on the through hole and athickness of the non vais-region ITO film layer located outside thethrough hole are the same.

Step S107: forming a photoresist layer on the ITO film layer;

wherein the photoresist layer is filled on the through hole. It can beunderstood that the present invention is not limited to form thephotoresist layer on the ITO film layer, another material layer can beformed on the ITO film layer. The requirement is to fill the ITO filmlayer. However, forming another material layer on the ITO film layerrequires another process for the material, which will increase themanufacturing process for the COA substrate in order to increase thecost. On the contrary, the manufacturing process for forming aphotoresist layer is very popular in the liquid crystal technologyfield. The present invention can adopt the manufacturing process formanufacturing the photoresist layer so as to reduce the manufacturingprocess for manufacturing the COA substrate to reduce the cost.

Step S108: performing a light-shielding process to the photoresist layeron the vias-region ITO film layer, and performing an exposure process tothe photoresist layer on the non vias-region ITO film layer.

In Step S108, the non vias-region ITO film layer includes a trace-regionITO film layer and a non trace-region ITO film layer. Performing apartial exposure process to the photoresist layer on the trace-regionITO film layer, and performing a full exposure process to thephotoresist layer on the non trace-region ITO film layer.

Specifically, using a nontransparent mask to perform the light-shieldingprocess to the photoresist layer on the vias-region ITO film layer inorder to maintain the thickness of the photoresist layer on thevias-region ITO film layer to be unchanged. Using a semi-transparentmask to perform a semi-exposure process to the photoresist layer on thetrace-region ITO film layer in order to partially remove the photoresistlayer on the trace-region ITO film layer. That is, decreasing athickness of the photoresist layer on the trace-region ITO film layer.Performing a full exposure process to the photoresist layer on the nontrace-region ITO film layer using a fully transparent mask in order tocompletely remove the photoresist layer non trace-region ITO film layer.

That is, after executing Step S108, the thickness of the photoresistlayer on the vias-region ITO film layer is unchanged, the thickness ofthe photoresist layer on the trace-region ITO film layer become thin,the photoresist layer on the non trace-region ITO film layer is removedcompletely.

It can be understood that when using a semi-transparent mask to performa process to the photoresist layer on the trace-region ITO film layer,through control a transmittance intensity of the mask, the thickness ofthe photoresist layer on the trace-region ITO film layer can be changed.Preferably, decreasing the thickness of the photoresist layer on thetrace-region ITO film layer to be half of an original thickness of thephotoresist layer on the trace-region ITO film layer. Of course,according to an actual requirement, controlling transmittance intensityof the mask, the thickness of the photoresist layer on the trace-regionITO film layer can be reduced to be one third, one quarter or twothirds, etc.

Step S109: developing the photoresist layer on the vias-region ITO filmlayer and the photoresist layer on the non vias-region ITO film layer.

In Step S109, using a developing solution to developing the photoresistlayer on the vias-region ITO film layer which has been performed thelight-shielding process and using the developing solution to developingthe photoresist layer on the non vias-region ITO film layer which hasbeen exposed.

In another embodiment, from Step S101 to Step S109 after developing, itcan perform the light-shielding process directly through the photoresistlayer on the vias-region ITO film layer, maintaining the photoresistlayer on the vias-region ITO film layer to be filled on the throughhole. Besides, through the photoresist layer on the non vias-region ITOfilm layer to perform exposing, removing the photoresist layer on thenon vias-region ITO film layer, and finally, a photoresist layer plugcovered on the vias-region ITO film layer can be obtained.

Step S110: using an etching process to remove the non trace-region ITOfilm layer.

That is, removing all of the non trace-region ITO film layer on thethird insulation layer.

Step S111: using a dry etching process to the photoresist layer on thetrace-region ITO film layer and the photoresist layer on the vias-regionITO film layer in order to completely remove the photoresist layer onthe trace-region ITO film layer, and partially remove the photoresistlayer on the vias-region ITO film layer such that the photoresist layerplug is covered on the through hole.

In Step S111, after performing a dry etching process to the photoresistlayer on the trace-region ITO film layer, the thinner photoresist layeron the trace-region ITO film will be removed completely to reveal thetrace-region ITO film layer which is patterned. At the same time, aportion of the thicker photoresist layer on the vias-region ITO filmlayer is remained in order to form the photoresist layer plug to blockthe through hole. The thickness of the photoresist layer on thetrace-region ITO film layer for removing and the thickness of thephotoresist layer on the vias-region ITO film for removing are the same.

In the present embodiment, because using a dry etching process to thephotoresist layer on the trace-region ITO film layer and the photoresistlayer on the vias-region ITO film layer, a side plane of the photoresistlayer plug exposed outside the through hole form a shape that isperpendicular to the base substrate. Because the side plane of thephotoresist plug is perpendicular to the base substrate, liquid crystalsnear the side plane of the photoresist layer plug will also beperpendicular to the base substrate, and will not change a tiltingdirection because of the affection of the photoresist layer plug. Whenthe side plane of the photoresist plug is not perpendicular to the basesubstrate, the side plane of the base substrate will form a largertilting angle such that the liquid crystals nearby will change thetilting direction because of the topography located so as to cause alocal abnormal display.

In the present embodiment, without adding a mask, using asemi-transparent mask (semi-exposure process) process to manufacture anITO electrode on a surface layer of the COA substrate, and using thephotoresist to fill the deeper through hole. That is, forming the ITOelectrode firstly, then, forming the photoresist on the ITO electrode tobe deposited in the through hole, which can optimize the displaymanufacturing process and effectively improve the panel quality.

Furthermore, the present invention discloses a display device, and thedisplay device includes a COA substrate. As shown in FIG. 3, the COAsubstrate includes a base substrate 10, a thin-film transistor, a secondinsulation layer 15, a color resist layer 16, a third insulation layer17, at least one through hole 20 which reveals a drain electrode of thethin-film transistor, an ITO film layer 18 and a photoresist layer plug19.

The thin-film transistor is disposed on the base substrate 10. Thesecond insulation layer 15 is disposed on the thin-film transistor. Thecolor resist layer 16 is disposed on the second insulation layer 15. Thethird insulation layer 17 is disposed on the color resist layer 16. TheITO film layer 18 is disposed on the third insulation layer 17, and theITO film layer 18 is attached on the through hole 20. That is, the ITOfilm layer 18 passes through the second insulation layer 15, the colorresist layer 16 and the third insulation layer 17, and connects with asignal of a drain electrode of the thin-film transistor. The photoresistlayer plug 19 is disposed on the through hole 20. The ITO film layer 18includes a vias-region ITO film layer disposed on the through hole 20and a trace-region ITO film layer. The trace-region ITO film layer isattached on the third insulation layer 17, and the vias-region ITO filmlayer is attached in the through hole 20. The photoresist layer plug 19is covered in the through hole 20 providing with the vias-region ITOfilm layer.

In the present embodiment, the thin-film transistor includes a firstmetal layer 11, a first insulation layer 12, a semiconductor activelayer 13 and a second metal layer 14. The first metal layer 11 isdisposed on the base substrate 10. The first insulation layer 12 isdisposed on the first metal layer 11. The semiconductor active layer 13is disposed on the first insulation layer 12. The second metal layer 14is disposed on the semiconductor active layer 13. The first metal layer11 forms a gate electrode of the thin-film transistor, and the secondmetal layer 14 forms a drain electrode and a source electrode of thethin-film transistor.

As shown in FIGS. 3 and 4, the photoresist layer plug 19 includes a plugportion 191 and a protrusion portion 192. The plug portion 191 is filledin the through hole 20, the protrusion portion 192 is protruded out fromthe through hole 20. In the present embodiment, the protrusion portion192 preferably includes a horizontal plane 194 in parallel with the basesubstrate 10 and a side plane 193 perpendicular to the base substrate10. Because the side plane 193 is perpendicular to the base substrate10, the liquid crystals near the side plane 193 will also beperpendicular to the base substrate 10, and will not change the tiltingdirection because of the affection of the side plane 193. At the sametime, the process to form the side plane 193 perpendicular to the basesubstrate 10 is convenient, directly using a dry etching process canform the side plane 193 perpendicular to the base substrate 10. When theside plane 193 is not perpendicular to the base substrate 10, forexample, the side plane 193 and the base substrate 10 form a largertilting angle, the liquid crystals nearby will change the tiltingdirection because of the topography located so as to cause a localabnormal display. Similarly, because the horizontal plane 194 is inparallel with the base substrate 10, the liquid crystals on thehorizontal plane 194 will be perpendicular to the base substrate 10, andwill not change the tilting direction.

In another embodiment, as shown in FIG. 5, a protrusion portion 292 inFIG. 5 can include a horizontal plane 294 in parallel with the basesubstrate 10 and a side plane 293 which forms an inclined angle with thebase substrate 10. Considering that the side plane 293 will affect thetilting direction of the liquid crystal, therefore, the inclined angleformed by the side plane 293 and the base substrate 10 in the presentembodiment is less than 30 degrees. Preferably, the inclined angleformed by the side plane 293 and the base substrate 10 is 20 degrees or15 degrees.

In summary, the side plane 193 of the protrusion portion 192 will affectthe deflection of the liquid crystals. In order to not affect thedeflection of the liquid crystals, in another embodiment, thephotoresist layer plug 19 can only include the plug portion 191, and theplug portion is directly filled in the through hole. The plug portion191 is provided with a horizontal plane in parallel with thetrace-region ITO film layer, that is a volume of the plug portion 191 isequal to a volume of the through hole 20 such that the plug portion 191is filled in the through hole 20, and the horizontal plane iscorresponding to a height of the trace-region ITO film layer.

In the present embodiment, through disposing the photoresist layer plugin the through hole of the COA substrate, it can prevents the liquidcrystals from gathering in the through hole through the photoresistlayer plug in order to improve the display effect, and the manufacturingprocess for the photoresist layer plug of the COA substrate is easily soas to optimize the manufacturing process of the panel and effectivelyimprove the panel quality.

The above embodiments of the present invention are not used to limit theclaims of this invention. Any use of the content in the specification orin the drawings of the present invention which produces equivalentstructures or equivalent processes, or directly or indirectly used inother related technical fields is still covered by the claims in thepresent invention.

What is claimed is:
 1. A method for manufacturing a color filter onarray (COA) substrate, comprising: forming a thin-film transistor on abase substrate, wherein the thin-film transistor comprises a first metallayer on the base substrate, a first insulation layer disposed on thefirst metal layer, a semiconductor active layer disposed on the firstinsulation layer, and a second metal layer disposed on the semiconductoractive layer, wherein the second metal layer forms a drain electrode ofthe thin-film transistor; forming a second insulation layer on thethin-film transistor; forming a color resist layer on the secondinsulation layer; forming a third insulation layer on the color resistlayer; and forming at least one through hole, which exposes the drainelectrode of the thin-film transistor, and which sequentially extendsthrough the third insulation layer, the color resist layer and thesecond insulation layer; wherein the method further comprises: formingan indium tin oxide (ITO) film layer on the third insulation layer,wherein the ITO film layer comprises a vias-region ITO film layerlocated on and attached in the through hole and a non vais-region ITOfilm layer located outside the through hole; forming a photoresist layeron the ITO film layer; performing a light-shielding process to thephotoresist layer located only on the vias-region ITO film layer, andperforming an exposure process to the photoresist layer on the nonvias-region ITO film layer; and developing the photoresist layer on thevias-region ITO film layer and the photoresist layer on the nonvias-region ITO film layer in order to obtain a photoresist layer plugonly covered on the vias-region ITO film layer; wherein the photoresistlayer plug comprises a plug portion and a protrusion portion, the plugportion is filled in the through hole, and the protrusion portion isprotruded out from the through hole and covers the through hole only;wherein the method further comprises assembling the COA substrate in adisplay device comprising a liquid crystal layer, wherein thephotoresist layer plug is in contact with a portion of the liquidcrystal layer near the photoresist layer plug; and wherein a side planeof the photoresist layer plug exposed outside the through hole isperpendicular to the base substrate.
 2. The method according to claim 1,wherein the non vias-region ITO film layer comprises a trace-region ITOfilm layer located adjacent to and outside the through hole and a nontrace-region ITO film layer located corresponding to the thin-filmtransistor; and wherein the step of performing an exposure process tothe photoresist layer on the non vias-region ITO film layer comprises:performing a partial exposure process to the photoresist layer on thetrace-region ITO film layer in order to partially remove the photoresistlayer on the trace-region ITO film layer, and performing a full exposureprocess to the photoresist layer on the non trace-region ITO film layerin order to completely remove the photoresist layer non trace-region ITOfilm layer.
 3. The method according to claim 2, wherein the step ofperforming a partial exposure process to the photoresist layer on thetrace-region ITO film layer comprises: using a semi-transparent mask toperform a semi-exposure process to the photoresist layer on thetrace-region ITO film layer.
 4. The method according to claim 2, whereinafter the step of developing the photoresist layer on the vias-regionITO film layer, the method further comprises: using an etching processto remove the non trace-region ITO film layer.
 5. The method accordingto claim 4, wherein after the step of using an etching process to removethe non trace-region ITO film layer, the method further comprises: usinga dry etching process to the photoresist layer on the trace-region ITOfilm layer and the photoresist layer on the vias-region ITO film layerin order to completely remove the photoresist layer on the trace-regionITO film layer, and partially remove the photoresist layer on thevias-region ITO film layer such that the photoresist layer plug is onlycovered on the through hole.